GB2591884A - A washer for a fixing for use on an enclosure - Google Patents

Abstract

A washer 14 has a first part annular portion 18 having concave and convex sides and a second part annular portion 24 having concave 22, 28 (i.e. inner) and convex 20, 26 (i.e. outer) sides. There is a linear connecting portion 30 joining the first and second part annular portions 18, 24 and a notch 34 formed on a side of the linear portion 30 closer to the concave sides 22, 28 of the part annular portions 18, 20. A pair of connectors 36, 38 is formed in distal ends of said part annular portions 18, 24 so that when the part annular portions 18, 24 are pressed towards each other the connectors 36, 38 lock together to form an annular washer. The washer 14 may be used with a threaded bolt in an enclosure for containing electrical components.

Description

A Washer for a Fixing for use on an Enclosure So present invention relates to a washer and relates particularly, but not exclusively, to a washer for retaining on 5 bolts to form a fixing which in turn are for use on an enclosure for electrical components.

The use of washers in combination with bolts is commonplace. Such washers can provide multiple functions, including distributing the load of the head of the bolt.

However, they can also act as a spacer or can ensure that the bolt is retained in engagement with a particular component even when it is not engaged with an internal thread. For example, bolts are commonly used to fix a lid to an enclosure, such as an enclosure for electrical components. In this example, the lid can be a sheet of metal with four apertures formed therein. Four bolts extend through these apertures and into threaded recesses formed the external surface of the enclosure around an opening which the lid closes. It is known to use shake proof or captive washers to retain the bolts in engagement with the apertures in the lid, even when the lid is not joined to the enclosure. These washers are provided with internally extending teeth which are slightly flexible and can flex sufficiently to allow the washer to be threaded onto the threaded portion of the bolt which at its head end has a non-threaded portion of a slightly smaller diameter than the distance across the thread. Once the bolt is in place and the washer has been threaded or forced over the thread onto the unthreaded portion, it is difficult for the bolts to pass back over the washer, meaning that the bolt is held in engagement with its aperture. This makes the process of fixing the lid to the enclosure significantly easier since all of the bolts are readily in position. This is particularly important when working at height as it reduces the risk of bolts being dropped. Furthermore, on -2 -a production facility such as a food processing line, the loss of a bolt or another component can result in the temporary closure of that line until the lost component is retrieved.

Although this function is useful, it is typically the case 5 that captive washers are formed from thin material and do not work effectively as spacers. Furthermore, although these washers are effective in keeping bolts in engagement with an aperture before the lid is brought into engagement with the enclosure, it is sometimes the case that when the lid has been engaged with the enclosure and it was removed that one of the internally facing teeth of the washer can become engaged with the thread of the bolt which ends up becoming unthreaded from the washer. Furthermore, it is a requirement of these washers that they are formed from a slightly springy material which can flex sufficiently to allow the teeth to engage the tread. However, the materials which are generally used in order to get the require flexion lack the anticorrosion properties required for clean environments or are extremely expensive to form in such low corrosion materials.

Another form of washer which, in common with the captive washer previously described, reduces the likelihood of the bolt becoming unthreaded through, for example, vibration is a split ring washer. These washers are much easier to form from thicker material, making them more useful as spacers, but they tend not to be able to act to capture the bolt in engagement with the lid. Furthermore, due to their exceptional thickness they are not flexible enough to capture and retain the bolt in engagement with the lid, they simply act to reduce the likelihood of a bolt being shaken free.

Preferred embodiments of the present invention seek to overcome or alleviate the above described disadvantages of the prior art. -3 -

According to an aspect of the present invention there is provided a washer for use with a bolt on a sealed enclosure, the washer comprising: a first part annular portion having concave and convex sides; 5 a second part annular portion having concave and convex sides; a connecting portion joining the first and second part annular portions, wherein said linear portion comprises a notch formed on a side of said linear portions closer to said concave sides of said part annular portions; a pair of connectors formed in distal ends of said part annular portions.

By providing a washer that can move from an open condition a closed condition by having a notch in a linear connecting portion which can close when a pair of connectors engage one another, the advantage is provided that a captive washer can be provided of any required thickness and can be formed from any suitable (particularly corrosion resistant) material. As a result, where the washer is used in conjunction with a bolt for fixing a lid to an enclosure it can ensure that the bolt does not separate from the lid even when the lid has been fixed and removed from the enclosure multiple times. The washer is therefore also able to act as a spacer and ensure that the lid is not over tightened onto the enclosure which can result in over compression, and therefore damage to, the seal.

In another preferred embodiment, the washer has a thickness between opposing planar surfaces of at least 3 mm.

According to another aspect of the present invention there is provided a fixing comprising: a bolt having a head and an external thread for engaging a 30 respective internal thread; and a washer as set out above. -4 -

In a preferred embodiment the bolt has an unthreaded portion between said head and said thread and, in use, said washer is located around said unthreaded portion.

Providing an unthreaded portion to the bolt has the advantage that the washer can be easily fitted over the bolt without damaging the thread and the size tolerance between the external portion of the bolt and the internal concave sides of the washer are not so critical to retain the washer in fixed engagement with the bolt.

According to a further aspect of the present invention there is provided an enclosure for containing electrical components, the enclosure comprising: a box having an opening; a lid for closing said opening and a plurality of apertures; a seal for sealing around a junction between said box and said lid; at least one fixing as set out above extending though a said aperture, wherein said box includes an internal thread for engagement with said external thread of said bolt, said washer is located on an inside of said lid and a head of said bolt is located on an outside of said lid and said washer limits compression of said seal.

In a preferred embodiment the washer engages opposing surfaces of said lid and said box.

By having the washer engaging the surfaces of the box and the lid the advantage is provided that the washer is not engaging the seal. This ensures the distance between the lid and the enclosure is precisely controlled (by the thickness of the washer) and this in turn very precisely controls the compression applied to the seal ensuring that it works most effectively and is not over compressed by the installer. -5 -

According to a still further aspect of the present invention there is provided a method of using a washer as set out above, comprising the steps: when said connectors are not engaged and said washer is in an 5 open condition, placing said concave surfaces of said washer around a bolt; applying a compression force to opposing said convex sides of said first and second part annular portions causing said connectors to engage one another and said notch to close thereby 10 moving said washer to a closed condition.

In a preferred embodiment when said washer is in said closed condition an internal diameter of said washer, measured between said concave sides, is greater than an external diameter of a cross section of said unthreaded portion and less than an external diameter of a cross section of said threaded portion.

In another preferred embodiment the washer is formed by cutting from a sheet of metal.

Forming the washer by cutting from a sheet of metal provides the advantage that the washer can be detected by metal detectors 20 which are used in food processing, although it is very unlikely that a washer of this type would become detached from the bolt In another preferred embodiment the cutting is performed by a CNC machine.

Preferred embodiments of the present invention will now be 25 described, by way of example only, and not in any limitative sense with reference to the accompanying drawings in which:-Figure 1 are plan and bottom views of a washer of the present invention in an open condition; Figure 2 is a plan and bottom views of the washer of figure 1 30 in a closed condition; -6 -Figure 3 is an isometric view of a fixing of the present invention with the washer of figure 1 in the open condition; Figure 4 is an isometric view of the fixing of figure 3 with the washer in the closed condition; and Figure 5 is an isometric view of an enclosure of the present invention incorporating the fixing of figure 4.

Referring to all of the figures, a fixing 10 is used in conjunction with an enclosure 12. The fixing 10 is formed from a washer 14 and a bolt 16. The washer 14 is cut from a sheet of stainless steel using a CNC machine. This allows the washer 14 to be formed with the shape shown in figure 1, which includes the following features. A first part annular portion 18 has an external convex side surface 20 and a concave internal side surface 22. Likewise, a second part annular portion 24 has an external convex side surface 26 and an internal concave side surface 28. Connecting these part annular portions is a short linear connecting portion 30 which creates a small planar surface 32 on the external side surface between the first and second convex side surfaces 22 and 26. On the Internal side, adjacent the first and second concave side surfaces 22 and 28, is a notch 34 which is substantially V-shaped. At the ends of the first and second part annular portions 18 and 24 that are distal of the linear portion 30 and notch 34 are a pair of connectors 36 and 38. Each of these connectors has a recess (respectively labelled 40 and 42) and a protrusion (labelled 44 and 46). These recesses and protrusions are sized and shaped to cooperate with each other when the washer 14 is in use, as will be described in further detail below.

The bolt 16 is typical in its formation of bolts known to persons skilled in the art having a head 48 and a threaded shaft 50. Between the head and threaded shaft is a non-threaded portion 52 of the shaft around which the washer 14 is fitted. The head 48 is provided with driving means in the form of a slot 54. It will be immediately apparent to persons skilled in the art that other driving means, including, but not limited to, cross head, hex head and Posidrive heads can be used.

Turning now to the enclosure 12, this example the enclosure is designed for use with electrical components and is shown in figure 5. The enclosure 12 includes an enclosure body 56 which has an opening 58 and a series of recesses 60 which are formed with internal threads. A rectangular lid 62 is also provided with a seal 64 extending around a periphery of the inner side of the lid. A series of four fixings 10 are provided in apertures formed adjacent to the corners of the rectangular lid 62.

The operation of the fixing 10, in particular when used in conjunction with the enclosure 12, will now be described. The washer 14 is formed in an open condition, as shown in figures 1 and 3 and is moved into a closed condition, as shown in figures 2 and 4 when it is located around the non-threaded portion 52 of the bolt 16. In the open condition the connectors 36 and 38 are separated and the V-shaped notch 34 is open. This allows the washer 14 to be placed around the bolt 16 and in particular around the non-threaded portion 52 of the shaft by passing the non-threaded portion through the gap between the connectors 36 and 38. Figure 3 shows the washer 14 having been engaged with the bolt 16 in this open condition. In order to move the washer from the open condition into the closed condition pressure is applied to the opposing convex side surfaces 20 and 24 and this pressure can be easily applied using a pair of pliers. The applied force results in the movement of the connectors 36 and 38 towards each other, which closes the V-shaped notch 34. The protrusions 44 and 46 are sized so that they come into contact with each other and in order to force the connectors 36 and 38 into full engagement with each other, (where the protrusions 34, sits in the recess 42 and the protrusion 46 sits in the recess 40) it is necessary for an additional force to be applied to the washer 14 in order to deform it sufficiently so that the protrusions pass over each other. Once the connectors are fully engaged with the protrusions 44 and 46 sitting in the recesses 5 42 and 40 respectively, the washer is now substantially annular with the V-shaped notch 34 closed. The planar surface 32 of the linear connecting portion 30 has bent to form a curved surface which is then approximately a continuation of the convex side surfaces 20 and 26, thereby forming a substantially circular 10 annulus.

With a bolt of the type shown in figures 3 and 4, the washer 14 is now captured on the bolt 16. This is because the diameter (labelled D1) measured across the concave side surfaces 22 and 28 of the washer in the closed condition is greater than the 15 diameter (labelled 52) of the non-threaded portion 52 of the bolt 16 but less than the diameter (labelled 53) across the outside of the threads of the threaded shaft 50. With the head 48 above and the thread 50 below the washer 14 is captive on the bolt 16. It is also worth noting that the shortest distance between the connectors 36 and 38 (labelled 54) is slightly greater than the diameter 52 of the non-threaded portion 52 of the bolt 16. This allows the washer 14 to be placed around the non-threaded portion 52 before it is closed using the snap fit closure mechanism previously described.

When used in conjunction with the lid 62, the bolts 16 are placed through the apertures in the lid, which aligned with the threaded recesses 60, and the washer 14 is then placed around the non-threaded portion 52 of the bolt 16 before being closed. As a result, the head 48 of the bolt 16 is located on one side of the lid (the outer side) and the washer 14 is located on the inner side, adjacent the seal 64, and the bolt 16 is therefore unable to be removed from engagement with the lid 62. When the enclosure body 56 has been mounted, typically to a wall and any _ 9 _ electrical components required inserted therein, the lid 62 can be brought into engagement with the enclosure to seal the components therein. The threaded shafts 50 of the bolts 16 are inserted into the recesses 60 so that the mutual threads can engage one another. A suitable driving device, such as a flat head screwdriver (not shown) is inserted into the slot 54 so as to drive the bolt 16 onto the thread of the recess 60. As the bolt 16 begins to tighten the lid 62 causes compression of the seal 64 until the washer engages the internal surface of the lid and the external surface of the enclosure body. Once the washer 14 is engaging both of these surfaces no further compression of the seal 64 can take place. As a result, the thickness of the washer (labelled D5) determines the compression of the seal 64 and this can be used to ensure the perfect sealing of the enclosure 12 by preventing over compression of the seal during installation.

It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the protection which is defined by the appended claims. In the example described above, the washer 14 occupies a space that is not in engagement with the seal 64 so that the washer engages the internal and external surfaces of the lid 62 and enclosure body 56 respectively to limit the compression of the seal as described above. This can be achieved by providing an aperture in the seal 64 which is larger than the external diameter of the washer (labelled D6). However, the washer 14 could engage the seal 64, although this would less effectively control the compression force applied to the seal. The bolt 16 does not necessarily have to have a non-threaded portion in order for the washer to be effective in controlling the compression of the seal 64. However, this will make the washer less effective as -10 -a captive washer which prevents the bolt from being separated from the lid.

Claims (10)

1. Claims 1. A washer for use with a bolt on a sealed enclosure, the washer comprising: a first part annular portion having concave and convex sides; 5 a second part annular portion having concave and convex sides; a linear connecting portion joining the first and second part annular portions, wherein said Linear portion comprises a notch formed on a side of said linear portions closer to said concave sides of said part annular portions; a pair of connectors formed in distal ends of said part annular portions.
2. 2. A washer according to claim 1, wherein said washer has a thickness between opposing planar surfaces of at least 3 mm.
3. 3. A fixing comprising: a bolt having a head and an external thread for engaging a respective internal thread; and a washer according to any of the preceding claims.
4. 4. A fixing according to claim 3, wherein said bolt has an unthreaded portion between said head and said thread and, in 20 use, said washer is located around said unthreaded portion.
5. 5. An enclosure for containing electrical components, the enclosure comprising: a box having an opening; a lid for closing said opening and a plurality of apertures; a seal for sealing around a junction between said box and said lid; at least one fixing according to claim 3 or 4 extending though a said aperture, wherein said box includes an internal thread for engagement with said external thread of said bolt, said 30 washer is located on an inside of said lid and a head of said -12 -bolt is located on an outside of said lid and said washer limits compression of said seal.
6. 6. An enclosure according to claim 5, wherein said washer engages opposing surfaces of said lid and said box.
7. 7. A method of using a washer according to claim 1 or 2, comprising the steps: when said connectors are not engaged and said washer is in a open condition, placing said concave surfaces of said washer around a bolt; applying a compression force to opposing said convex sides of said first and second part annular portions causing said connectors to engage one another and said notch to close thereby moving said washer to a closed condition.
8. 8. A method according to claim 7, wherein when said washer is in said closed condition an internal diameter of said washer, measured between said concave sides, is greater than an external diameter of a cross section of said unthreaded portion and less than an external diameter of a cross section of said threaded portion.
9. 9. A method according to claim 8, wherein said washer is formed by cutting from a sheet of metal.
10. 10. A method according to claim 9, wherein said cutting is performed by a CNC machine.